The present invention is directed to compound archery bows, and more particularly to a so-called single-cam compound archery bow having a power let-off cam mounted on the end of only one of the bow limbs.
Compound archery bows typically are of the so-called dual-cam design, originated in U.S. Pat. No. 3,486,495. Bows of this type typically comprise a bow handle having limbs mounted on and extending from opposed ends of the handle. Power let-off cams are rotatably mounted on the free ends of the bow limbs, and are interconnected by one or more cable sections including a draw string section. As the bow draw string is drawn away from the handle, draw force initially increases as the limbs are drawn together and the cams rotate to a power let-off point, and thereafter the leverage increases and the draw force decreases as the cams rotate further but with little additional limb flexure. This so-called compound action allows full bow draw to be maintained at lesser force without fatigue to the archer. A problem inherent in dual-cam bows of this type lies in the fact that the cams must be closely matched and synchronized with each other in order to insure straight-line (or substantially straight-line) travel of the nock point on the bowstring, and the limbs must be closely balanced and evenly stressed as the string is drawn. Damage to or mismatch of the cams, mismatch or incorrect adjustment of the limbs, or stretching of the cable sections can cause loss of synchronization between the cams and uneven stressing of the limbs, resulting in less than optimum performance of the bow and erratic arrow flight.
In order to overcome the aforementioned deficiencies of dual-cam bows, it has heretofore been proposed to provide a compound bow that has a single power let-off cam disposed at the end of one bow limb, and a control pulley or wheel disposed at the end of the opposing limb over which the bowstring is trained. U.S. Pat. No. 5,505,185 discloses such a single-cam compound bow. A control cable cooperates with a power let-off cam and a control groove in the control wheel or a second let-out groove on the power cam to maintain the desired relationship or timing between bowstring let-out grooves in the control wheel and power cam. In this way, identical or substantially identical incremental bowstring cable travel to and from the bowstring let-out grooves is obtained, thereby yielding straight-line nock travel as the bowstring cable is drawn and released. A power cable extends from the power cam to the opposing bow limb for flexing the blow limbs uniformly as the bowstring is drawn, and for cooperating with the power cam to obtain the power let-off action that is characteristic of compound bows.
Although the single-cam compound bow disclosed in the noted patent addresses and overcomes many problems theretofore extant in the art, further improvements remain desirable. In particular, the noted patent does not disclose any means or technique for adjusting draw length of the bow. That is, the bow disclosed in the noted patent obtains straight-line nock travel for a given bow draw length for which the power cam and the control wheel or the second let-out groove of the power cam are designed. In order to change or adjust bowstring draw length, the power cam and/or the control wheel must be changed to accommodate the new desired draw length while maintaining synchronous timing between the cam and wheel. In a commercial single-cam compound bow of a different design, accommodation is made for changing the bowstring cable anchor point at the power let-off cam, and thereby changing the bowstring draw length. However, since the cams and wheels are optimized for only a single draw length, changing the bowstring anchor point inherently changes the path of nock travel as the bow is drawn and released, and consequently affects shootability of the bow.
U.S. Pat. 5,934,265 discloses a single-cam compound archery bow that includes a bow handle from which bow limbs project, a control wheel rotatably mounted on one end of one limb and a power cam rotatably mounted at an opposing end of the other limb. A power cable segment is anchored at one end to the one limb and at a second end to the power cam at a position to wrap into and unwrap from a power cable groove on the power cam. A bowstring cable segment is anchored to the control wheel and to the power cam at positions to wrap into and unwrap from first and second bowstring let-out grooves on the control wheel and the power cam respectively. The bowstring cable segment has a nock point disposed between the spaced limb ends. A control cable segment is anchored at one end to the control wheel at a position to wrap into and unwrap from a control groove on the control wheel, and is anchored at an opposing end to the power cam. As the bowstring cable segment is drawn away from the handle, the bowstring cable segment unwraps equally from the control wheel and power cam, wraps the power cable segment into the power cable groove on the power cam so as to draw the bow limb ends together to a power let-off point at the power cable groove, and wraps the control cable segment into the control groove on the control wheel. Length of the power cable groove on the power cam, and position of the power let-off point on the power cam, are adjustable while maintaining a fixed separation between the power let-off point and the control cable anchor on the power cam, so that the nock point travels in a straight line as the bowstring cable section is drawn and released independent of adjusted length of the power cable groove and position of the power let-off point.
U.S. Pat. No. 5,934,265 also describes an embodiment in which the bowstring cable segment and the control cable segment form a continuous length that is trained around a pulley having a single groove that is concentric with the axis of pulley rotation. The cable is not anchored to the pulley. Such an arrangement does not provide desired control of nock point travel, control cable let-out or bow energy storage. U.S. Pat. No. 6,082,347 discloses a single-cam compound archery bow in which, in the preferred embodiments, provision is made at both the power cam and the control wheel for adjusting bowstring cable draw length. Furthermore, timing indicia are provided on both the power cam and the control wheel for selective registry with the control cable segment on the control wheel and the power cable segment on the power cam to fine-tune adjustment of nock point travel.
A single-cam compound archery bow in accordance with a first aspect of the present invention includes a bow handle having projecting limbs. A control wheel is mounted for rotation about an axis at an end of one of the limbs, and has a single peripheral groove that extends around such axis. A power cam is mounted for rotation at an end of the other limb. A bow cable arrangement includes a first cable segment anchored at one end to the one limb and at a second end to the power cam. A second cable segment is anchored to the control wheel and extends to the power cam. A third cable segment is anchored to the control wheel and extends to the power cam. The third cable segment includes a nock point that, when drawn away from the handle, unwraps the third cable segment from the control wheel groove, and wraps the second cable segment into the control wheel groove as the third cable segment is unwrapped from that groove. Drawing of the nock point away from the handle also wraps the first cable segment onto the power cam so as to draw the limbs together. The single peripheral groove in the control wheel preferably lies in a plane perpendicular to the axis of rotation of the control wheel.
A single-cam compound archery bow in accordance with a second aspect of the invention includes a bow handle having projecting limbs, a control wheel mounted on an end of one of the limbs for rotation about an axis, and a power cam rotatably mounted on an end of the other limb. The control wheel has a peripheral control wheel groove in a plane perpendicular to the axis of rotation of the control wheel. The power cam includes a bowstring groove and a power cable groove. A bow cable arrangement includes a power cable segment anchored at one end at the axis of rotation of the control wheel, and at a second end to the power cam at a position to wrap into and unwrap from the power cable groove. A bowstring cable segment is anchored at the control wheel at a position to wrap into and unwrap from the control wheel groove, and is anchored at the power cam at a position to wrap into and unwrap from the bowstring groove on the power cam. A control cable segment is anchored at the control wheel at a position to wrap into and unwrap from the control wheel groove, and is anchored at the power cam. As the bowstring cable segment is drawn away from the handle, the bowstring cable segment unwraps from the bowstring groove and the control wheel groove, the control cable segment wraps into the control wheel groove as the bowstring cable segment unwraps therefrom, and the power cable segment wraps into the power cable groove on the power cam to draw the limbs together. The control cable segment and the bowstring cable segment may comprise separate cable segments separately anchored at the control wheel, or may comprise a single length of bow cable anchored at the control wheel effectively to divide the cable length into separate control cable and bowstring cable segments. The peripheral groove on the control wheel may be either circular or non-circular, and may be either concentric with or non-concentric with the axis of rotation of the control wheel.
A control wheel for a single-cam compound archery bow in accordance with another aspect of the present invention includes a body for mounting on a bow limb to rotate about an axis, and a single peripheral groove surrounding the axis and lying in a plane perpendicular to the axis. The single peripheral groove includes a gap, and one or more anchors are disposed radially inwardly of the gap for anchoring bow cable segments to wrap into and unwrap from portions of the groove on opposite sides of the gap. The peripheral groove may be either circular or non-circular, and may be either concentric with or non-concentric with the rotation axis. The anchor(s) may be such as to anchor separate cable segments to the control wheel, or to anchor a single length of cable to the control wheel while effectively dividing the length into separate cable segments.